New fire pit on natural blue stone patio.

20" by 20" by 6" deep

1) I am planning to load lava rocks on bottom to reduce overall costs since glass expensive. What are implications to aesthetics with this idea? (both lit at night and daytime unlit)

2) Any differences (besides obvious) between cut glass verse softer shaped glass drops?

3) Any suggestions on colors. The hot tub as some colored lights at night. I don't want it to look like a night club at night but wondering if i combine a few colors like aqua, clear, bronze or copper color?